Alterations of the trabecular pattern of the jaws in patients with osteoporosis

Fractal dimension and lacunarity analysis of dental radiographs

OBJECTIVE

As the occlusal forces transmitted to the jaw bones during mastication might be different in dentate and edentulous regions, there might be different radiographical trabecular bone texture in these regions. Image analysis procedures are promising techniques which are used to detect structural changes of bone texture on radiographs. In this study, the differences of fractal dimension (FD) and lacunarity measurements of radiographical trabecular bone between dentate and edentulous regions were investigated.

METHODS

Direct digital radiographs of premolar-molar region were taken from 51 patients who were included in our study. Two rectangular regions of interest (ROIs) with the same dimensions (37x119 pixels) were created on these radiographs; one in the edentulous region and the other one in the dentate region. The ROIs were segmented as black and white areas. Box-counting fractal dimension and lacunarity of these regions were calculated.

RESULTS

Paired samples t-test and Pearson correlation coefficients were calculated. It was found that there were differences between dentate and edentulous regions for FD and lacunarity (P=0.000). There is a negative correlation between FD and lacunarity (-0.643, P<0.01), positive correlation between dentate and edentulous regions and FD (0.819, P<0.01), and a negative correlation between lacunarity and dentate and edentulous regions (-0.541, P<0.01).

CONCLUSIONS

The differences of occlusal forces generated in dentate and edentulous regions during mastication cause some alterations in trabecular bone structure, and fractal dimension and lacunarity can reveal these alterations quantitatively.

Change in mandibular trabecular pattern and hip fracture rate in elderly women

OBJECTIVES

To determine if alterations of trabecular pattern, or the rate of change of jaw trabeculae, are associated with rate of hip fracture.

METHODS

Participants in a population-based study of residents of a California retirement community (Leisure World Cohort Study) were asked for permission to obtain their dental radiographs. Periapical radiographs were retrieved on 598 women (average age at time of first radiograph=77 years). Several measurements of trabecular pattern (strut analysis), textural properties (run-length analysis) and Fourier analysis were made in several anatomical regions of the jaw. These trabecular features and clinical information self-reported by subjects in the early 1980s were examined for association with hip fracture rate using Cox proportional-hazard regression.

RESULTS

Rate of hip fracture increased with decreasing average length of node-to-terminus struts in the mandibular incisor region. Each 0.01 mm per year decrease in the average length of node-to-terminus struts increased hip fracture rate by a factor of 2.9 (P=0.02, accuracy=73%). Inclusion of clinical parameters improved the predictive model compared with use of the radiographic parameter alone (accuracy=79%). Similar results were seen for percent change per year in this parameter.

CONCLUSIONS

Changes in radiographic trabecular structure, augmented with clinical information, are predictive of hip fracture in elderly women. Further refinement of both the radiographic and clinical parameters may lead to a screening process accessible to a large number of women and to early diagnosis and treatment of osteoporosis.

Clinical and panoramic predictors of femur bone mineral density

Dentists are a potentially valuable resource for initial patient screening for signs of osteoporosis, as individuals with osteoporosis have altered architecture of the inferior border of the mandible as seen on panoramic radiographs. Our aim was to evaluate the efficacy of combining clinical and dental panoramic radiographic risk factors for identifying individuals with low femoral bone mass. Bone mineral density was measured at the femoral neck and classified as normal, osteopenic or osteoporotic using WHO criteria in 227 Japanese postmenopausal women (33-84 years). Panoramic radiographs were made of all subjects. Mandibular cortical shape and width was determined and trabecular features were measured in each ramus. Mean subject age, height, and weight were significantly different in the three bone-density groups (P<0.0001). A classification and regression trees (CART) analysis using just clinical risk factors identified 136 (87%) of the 157 individuals with femoral osteopenia or osteoporosis. Mean mandible cortical width (P<0.0001), cortical index (P<0.0001) and trabecular features (P=0.02) were also significantly different in the three bone density groups. A CART analysis considering only radiographic features found 130 (83%) of the 157 individuals with femoral osteopenia or osteoporosis, although none of the subjects with osteoporosis was correctly identified. A CART analysis using both clinical and radiographic features found that the most useful risk factors were thickness of inferior border of the mandible and age. This algorithm identified 130 (83%) of the 157 individuals with femoral osteopenia or osteoporosis. The results of this study suggest that 1) clinical information is as useful as panoramic radiographic information for identifying subjects having low bone mass, and 2) dentists have sufficient clinical and radiographic information to play a useful role in screening for individuals with osteoporosis.

The effect of ovariectomy on mandibular cortical thickness in the rat

OBJECTIVES

The purpose of this study was to investigate the effects of long-term oestrogen deficiency on mandibular cortical thickness in ovariectomized rats.

METHODS

Twelve female rats either underwent ovariectomy or received a sham-operation. One year later images of the left side of the mandible were made using a standardized radiographic protocol. Manual measurements were made of the lower mandibular cortical thickness at three locations. The mean cortical thickness was also assessed using a specially developed image analysis program by placing points at three positions, identical to those used for the manual measurements, and additionally at 20 points evenly distributed along the mandibular cortex.

RESULTS

The mean mandibular cortical thickness of the ovariectomized mandibles was significantly less than that of the sham-operated rats, measured using the computer image analysis (p=0.016, 95% CI=0.125, 0.016) and measured manually (p=0.011, 95% CI=0.0218, 0.1309). When 20 computational points were used, the mean mandibular cortical width of the ovariectomized rats was significantly less than that for the control rats (p=0.016, 95% CI=0.127, 0.018).

CONCLUSIONS AND CLINICAL IMPLICATIONS

Long-term oestrogen deficiency in ovariectomized rats decreased the mandibular cortical thickness. If our result is applicable to human studies, a considerable duration of oestrogen deficiency may be necessary before a reduction of mandibular cortical bone loss can be observed. Because mandibular cortical bone is resistant to resorption, the value of clinically determined mandibular cortical thickness measurements as a method of detecting patients at risk of osteoporosis may have a reduced importance in younger postmenopausal patients.

Maxillary bone mineral density and its relationship to the bone mineral density of the lumbar spine and hip

OBJECTIVE

We sought to measure the bone mineral density (BMD) of various regions in the maxilla before implant treatment and to investigate correlations between these values and the BMDs of the spine and hip.

STUDY DESIGN

Eighteen patients were examined by means of quantitative computed tomography, and the BMD of the maxillary alveolar ridge was calculated. The same patients also underwent dual-energy x-ray absorptiometry of the lumbar spine and the total hip. Analysis of variance was used to compare BMD values between and within individuals. The Pearson correlation coefficient was used to correct for sex and body mass and to calculate the correlation between the BMD of the maxillary alveolar ridge and the BMD of the spine and hip.

RESULTS

The maxillary BMD varied significantly between individuals (P <.001) and within individuals (P <.001). The BMD of the anterior region of the maxilla was correlated significantly with the BMD of the lumbar spine (r=0.6; P <.05).

CONCLUSION

A site-specific evaluation of maxillary bone tissue could be of value before implant treatment.

Fourier and wavelet analyses of dental radiographs detect trabecular changes in osteoporosis

OBJECTIVES

Osteoporosis results in loss of bone mass and microarchitectural deterioration. Dental radiographs potentially offer a means of screening for osteoporosis as they are commonly made on adults. Spatial frequency analyses are well suited to detect subtle changes in image patterns. We hypothesize that individuals with osteoporosis exhibit an altered radiographic trabecular pattern that can be detected by spatial frequency and strut analysis.

STUDY DESIGN

Maxillary and mandibular periapical radiographs of 26 women with osteoporosis and 23 controls were examined using one-dimensional discrete Fourier and wavelet analyses in both jaws to measure the spatial frequency distributions of trabecular structures. A strut analysis was also performed.

RESULTS

Individuals with osteoporosis revealed an altered trabecular pattern compared to controls. Using Fourier and strut variables allows classification of subjects with 92% sensitivity, 96% specificity, and a 22% cross-validation error rate. Wavelet analysis was also useful but did not perform better than Fourier analysis for subject classification.

CONCLUSIONS

Spatial frequency analysis of digitized dental radiographs, especially Fourier analysis, and strut analysis provide value for identifying individuals with osteoporosis.

Effects of oestrogen deficiency on rat mandibular and tibial microarchitecture

OBJECTIVES

To investigate the effects of oestrogen deficiency on the microarchitecture of trabecular bone in the mandible and the tibia and to test whether they are correlated.

METHODS

Twenty-four age-matched Lewis-Brown-Norway female rats underwent surgical intervention either to remove ovaries (ovariectomy, n=12) or to create a complementary control group (sham-operated, n=12). Sixteen weeks later, the animals were sacrificed and the left side of the mandibles and the tibias were scanned with high resolution micro-CT (15 micro m). Multiple morphological measures including the ratio of bone volume/tissue volume, trabecular thickness, trabecular separation and structure model index were obtained from the experimental and control groups.

RESULTS

Ovariectomy significantly decreased the ratio of bone volume/soft tissue volume and trabecular thickness, whilst significantly increasing trabecular separation and structure model index in the mandible (P<0.005) and the tibia (P<0.005). There were significant positive correlations between the mandible and the tibia for trabecular separation (r=0.68, P<0.01) and structure model index (r=0.60, P<0.01).

CONCLUSIONS

Oestrogen deficiency results in microarchitectural alterations of trabecular bone in both the mandible and the tibia within 16 weeks. The size of marrow spaces and the shape of trabeculae in the mandible correlate with osteoporotic changes in the long bone.

Digital Image Analysis of Cadaver Mandibular Trabecular Bone Patterns

BACKGROUND

The purpose of this study was to investigate the source of radiographic trabecular patterns by removing trabecular bone in four sequential steps from six cadaver mandible sections, radiographing the sections after each removal, and using four digital-image analysis methods to quantify any resulting changes to the radiographs.

METHODS

Mandible sections were cut sagittally into halves. Trabecular bone was removed from each section in four stages. Following each stage, standardized radiographs were taken, using direct digital equipment. Trabecular bone in the resulting digital images was measured with four methods. Mean gray level values (method 1) and cumulative percent histograms (method 2) were calculated from the raw data. Morphological image processing was used to skeletonize the trabecular structure, which was quantified by counting the number of trabecular ends and segments in the skeletonized images (method 3) and performing fractal analyses of the skeletonized images (method 4). Repeated measures analysis of variance (ANOVA) was used to test for changes in measurements attributable to bone removal.

RESULTS

Repeated measures ANOVA indicated that the use of gray levels, cumulative percent histograms, and morphologic operators resulted in highly significant changes in measurements following bone removal (P < 0.01). Ends and segments demonstrated similar performance, with changes highly significant over time (P < 0.01). Fractal analysis also resulted in highly significant changes over time (P < 0.01).

CONCLUSIONS

The analyses performed in this study demonstrated consistent image differences following the four steps of bone removal. These differences appeared whether light, cancellous bone or heavier endosteal bone was removed. These findings indicate that trabecular and endosteal bone combine to form the structure that most dentists identify as trabeculae on intraoral radiographs.

Long-term changes in trabecular structure of aged rat alveolar bone after ovariectomy

OBJECTIVE

Trabecular structural changes in the jaw after long-term estrogen deficiency are not well understood. Therefore, we sought to observe the changes in rat alveolar bone for 1 year.

METHODS

Six-month-old female rats were ovariectomized (OVX) or underwent a sham operation. After 1 year, bone histomorphometry and a node-strut analysis were performed on the interradicular septum of the mandibular first molar by using micro computed tomography and confocal laser scanning microscopy. Statistical analysis was carried out by using analysis of variance.

RESULTS

The alveolar trabeculae of rats in the sham group had network structures, whereas the trabeculae of rats in the OVX group became fragmented. The trabecular bone volume, number, and thickness in the OVX group were significantly lower than those found in the sham group, and the trabecular separation was 4-fold higher in the OVX group than in the sham group. Bone resorptive and formative activity appeared to be moderately higher in the OVX group than in the sham group, but only the difference in bone formation was of statistical significance.

CONCLUSION

By 1 year after ovariectomy, bone loss and trabecular fragmentation had occurred in the rat mandibular alveolar bone.

Fractal analysis of mandibular bony healing after orthognathic surgery

OBJECTIVES

We evaluated the radiographic changes to the operational sites after orthognathic surgery by using fractal analysis.

STUDY DESIGN

Panoramic radiographs from 35 patients who underwent orthognathic surgery on the mandible without any complications during the osseous healing process were selected. The radiographs taken before the operation (stage 0) and 1 or 2 days (stage 1), 1 month (stage 2), 6 months (stage 3), and 12 months (stage 4) after the operation were digitized at 600 dpi with 256 gray levels. The fractal dimension was calculated by means of a tile-counting method in the region of interest centered on the operational site and was statistically analyzed according to its stages.

RESULTS

The fractal dimension was decreased immediately after the operation and increased gradually according to the time lapse (P <.05). The fractal dimension in the region of interest 12 months postoperatively was similar to that preoperatively.

CONCLUSION

This result suggests that fractal dimension can be used to evaluate the bony healing process after orthognathic surgery.

Oral radiographic predictors of osteoporosis

Osteoporosis is a systemic skeletal disease characterized by low bone mass and micro architectural deterioration of the bone scaffold that result in increased bone fragility and susceptibility to fracture. It is one of the most common disorders of the elderly and is estimated to effect 75 million people in Europe, Japan and the USA. The purpose of screening for osteoporosis is to identify individuals who are likely to benefit from treatment. The fact that dental radiographs are regularly made on a large fraction of the adult population makes their potential use as a marker of skeletal health an exciting avenue of research. In the last four decades numerous research teams have reported oral radiographic findings associated with osteoporosis. The preponderance of the evidence shows that the jaws of subjects with osteoporosis show reduced bone mass and altered morphology. Clinically useful predictions of individuals most likely to develop osteoporotic fractures will require a multifactorial model including both radiographic and clinical findings. Future efforts should continue to search for oral radiographic signs with high sensitivity and specificity for osteoporosis, identify clinical signs available in the dental office associated with osteoporosis, develop multidisciplinary classification methods including both radiographic and clinical parameters, and automate radiographic and clinical analyses as much as possible to minimize the involvement of the dentist as well as to standardize data collection.

The physiology, medical management and oral implications of menopause

BACKGROUND

Approximately 36 million women in the United States are in the postmenopausal phase of life. The vast majority of these women experienced spontaneous cessation of menses between the ages of 47 and 55 years when the production of estrogen decreased because of an inadequate number of functioning follicles within their ovaries. Fewer women entered menopause after surgical removal of both ovaries. This procedure usually is performed prophylactically to prevent ovarian cancer in conjunction with a hysterectomy, which is required to treat abnormal bleeding, endometriosis or pelvic inflammatory disease. The physiological changes associated with spontaneous or surgical menopause cause some women to experience uncomfortable symptoms such as hot flashes, night sweats and vaginal dryness. In addition, estrogen deprivation arising from menopause in association with age-related factors disproportionately increases the risk of developing cardiovascular disease (that is, myocardial infarct, stroke), osteoporosis, Alzheimer's disease and oral disease. Hormone replacement therapy, or HRT (estrogen or estrogen and progestin), often is prescribed on a short-term basis to alleviate the uncomfortable symptoms associated with estrogen deficiency and on a long-term basis to prevent some of the chronic illnesses common to postmenopausal women.

CONCLUSIONS

Dentists who treat women entering menopause need to consider the stressful phase of life their patients are experiencing. Clinical findings of postmenopausal problems on dental examination may include a paucity of saliva, increased dental caries, dysesthesia, taste alterations, atrophic gingivitis, periodontitis and osteoporotic jaws unsuitable for conventional prosthetic devices or dental implants. Panoramic dental radiographs may reveal calcified carotid artery atheromas.

CLINICAL IMPLICATIONS

Dentists have an opportunity to refer women who are not under the care of a gynecologist for an evaluation to determine the appropriateness of HRT for its systemic and oral health benefits.

Estimation of skeletal bone mineral density by means of the trabecular pattern of the alveolar bone, its interdental thickness, and the bone mass of the mandible

OBJECTIVE

We sought to evaluate the use of the alveolar trabecular pattern, the mandibular alveolar bone mass (MABM) measured by photodensitometry, and the interdental alveolar thickness for prediction of the skeletal bone mineral density (BMD).

STUDY DESIGN

MABM and the coarseness of trabeculation were assessed by using periapical radiographs in 80 dentate women. The interdental alveolar thickness was measured on casts, and BMD of the forearm with dual X-ray absorptiometry.

RESULTS

Significant correlations were found between skeletal BMD and MABM (r = 0.46, P <.001) as well as the coarseness of the trabeculation (r = 0.62, P <.001). The interdental alveolar thickness improved the correlation between skeletal BMD and MABM (R2 = 0.44, P <.001). Age, but not interdental thickness, improved the correlation between the coarseness of trabeculation and skeletal BMD (R2 = 0.52, P <.001).

CONCLUSION

Evaluation of the coarseness of trabeculation of the alveolar bone as seen on intraoral radiographs is a helpful clinical indicator of skeletal BMD and better than densitometric measurements of the alveolar bone. Dense trabeculation is a strong indicator of high BMD, whereas sparse trabeculation may be used to predict low BMD.

Comparison of 5 protocols based on their abilities to use data extracted from digitized clinical radiographs to discriminate between patients with gingivitis and periodontitis

BACKGROUND

This study was undertaken to compare 5 digital analytic protocols for their abilities to extract data from digital clinical radiographs and discriminate between patients with gingivitis and periodontitis.

METHODS

Five digital-image analysis protocols were compared for their abilities to discriminate between two groups of 24 patients each. One group was diagnosed with healthy gingiva (or gingivitis) and the second with periodontitis. These groups were previously evaluated in published studies that used fractal and morphologic analyses. Pre-existing clinical radiographs for each patient were digitized and regions of interest (ROIs) were placed on interdental bone in mandibular posterior quadrants. The 5 protocols used were: 1) MGB: a median filtration to remove high-frequency noise, a Gaussian filtration to remove low-frequency noise, binarization of the resulting image, and quantification of the black pixels; 2) MGBS: the same protocol as MGB except for a skeletonization of the binary image and a quantification of the skeleton's pixels; 3) GBS: Gaussian filtration, binarization (thresholding on the mean pixel value) of the resulting image, skeletonization, and quantification of the pixels of the skeleton; 4) NS: normalization, skeletonization, and quantification of the skeleton's pixels; and 5) S: a variation of NS, except normalization was not used. The resulting values for the 2 patient groups were compared with Mann-Whitney U tests and effect likelihood-ratio test.

RESULTS

For digitized radiographs, the mean gray-scale value (+/- standard deviation) for gingivitis patients was 183.22 +/- 18.53 and for periodontitis patients 181.26 +/- 17.20. Mann-Whitney U tests resulted in the following P values for these protocols: MGBS <0.01; S <0.01; GBS <0.01; NS <0.01; and MGB <0.83. Effect likelihood-ratio tests indicated that only MGBS and S significantly contributed to models containing the other factors.

CONCLUSIONS

Small variations to protocols affected the strength of the discrimination between the gingivitis and periodontitis groups. While there is potential for morphologic analysis to be used to discriminate between patients with gingivitis and periodontitis, a robust technique was not identified.